A riding mower chassis of the type to which this invention relates is mainly intended for carrying and powering a rotary lawn mower, although it may also tow a light trailer and carry certain unpowered equipment such as a clipping receptacle. Such a riding mower chassis is distinguished from a lawn tractor, which has a front mounted engine and which can carry interchangeable implements that are powered by its engine, such as a lawn mower, a snow blower or a tiller. For many applications the lesser versatility of the riding mower chassis is more than compensated for by its being more compact, lighter and substantially less expensive than a comparable lawn tractor. Nevertheless, it is obviously desirable for a riding mower chassis to be cooperable with a variety of useful accessories, especially if it can be given such capability without significant increase in its cost.
U.S. Pat. No. 2,924,928, to Rhoades et al, discloses a riding mower chasis of the general type to which this invention relates. However, on that chassis the mower was mounted between the front and rear wheels, and the front wheels were steerable while the rear wheels were power driven. The mower chassis of this invention, by contrast, is intended for a mower that is mounted in front of the front wheels, and its front wheels are driven while its rear wheels are steerable. A front mounted mower has the important advantage that it can operate under lowhanging bushes and the like, to trim areas that would be inaccessible to a mower mounted under the middle of the chassis. The driven front wheels and steerable rear wheels ensure good traction and a short turning radius, to provide maneuverability for satisfactory mowing in a confined space.
U.S. Pat. No. 4,384,443, to Hoogstrate, discloses a mowing machine chassis having front traction wheels and steerable rear wheels, wherein the front wheels were driven from an engine mounted over the rear wheels, behind the operator's seat. This arrangement was lacking in compactness because power inputs had to be transmitted along the full length of the chassis from the rear-mounted engine to the front traction wheels, while steering inputs had to be transmitted to the rear wheels from a steering wheel at the very front of the chassis. Furthermore, because of the rear-mounted engine, no useful cargo could be carried behind the operator's seat.
Unlike the machines of the two patents discussed above, the riding mower chassis of this invention, although of desirably short overall length, has a load supporting platform tiltably mounted behind its operator's seat, for supporting a dump body or any of various other accessories such as a clipping receptacle, a fertilizer spreader or a sprayer tank.
U.S. Pat. No. 4,429,515, to Davis, Jr. et al, discloses a mower chassis for a front mounted mower, having its engine mounted between the front wheels and the rear wheels and its operators's seat supported over the engine. Behind the engine was tiltable hopper for supporting a grass clipping receptacle or other cargo. The chassis had a tripod support on laterally spaced front propulsion wheels and a castered dual rear wheel. Steering was effected by individual control of the front wheels, each of which had its own independent hydraulic motor. This arrangement undoubtedly afforded extreme maneuverability, but it was also relatively expensive because of its need for a hydraulic system that included a pump as well as the two hydraulic wheel-driving motors and their controls.
With any riding mower having a pair of laterally spaced swivelingly steered wheels, whether such wheels are at its front or at its rear, it is essential for satisfactory traction and maneuverability that all four wheels be maintained in constant engagement with the ground notwithstanding irregularities in the terrain. To this end the steerable rear wheels of the chassis of this invention are mounted on an axle which is tiltable relative to the chassis frame about an axis parallel to the longitudinal centerline of the chassis. If the chassis is carrying no load other than the mower and the operator, it is often desirable to install weights over the rear wheels to maintain them in good steering engagement with the ground. Quick and easy installation and removal of such weights is obviously desirable, but it is also important that the weights, when installed, should be securely fastened to the frame, be as close as possible to ground level, and not to interfere with tilting of the load supporting platform or with any load that may be carried on it.
It will be apparent that the above mentioned requirements and desiderata should be obtained in a mower chassis that has a frame which is extremely sturdy and rigid but is nevertheless simple, inexpensive, and as light as possible.